HARLINGEN — A $158,000 project at Hugh Ramsey Nature Park will filter runoff to help improve the waters of the Arroyo Colorado.

City officials have closed the park through Feb. 1 as crews build a bio-retention basin on its parking lot.

The 100-foot by 8-foot basin will filter motor oil and other chemicals before the runoff streams through wetlands and flows into the arroyo.

“I don’t know of any other place with bio-retention like this,” Javier Mendez, the city’s park’s director, said Tuesday.

A $158,000 grant from the Texas General Land Office’s Coastal Impact Assistance Program will fund the project.

Made up of layers of bull rock and soil, the retention basin will act as a natural filter.

Underground piping will carry the water through a network of ponds and wetlands before it is discharged into the arroyo.

“That’s a neat project,” Jeff Lyssy, the city’s park’s supervisor, said. “It will trap oil and other hazardous chemicals, filter the water and slowly release it through wetlands to improve the water quality of the arroyo.”

When crews complete the project, Mendez said, native trees and shrubs like wild olive and sage will stand over the retention basin.

“Aesthetically, it will add native plants that will hopefully attract birds and butterflies,” Lyssy said.

For years, the Lower Rio Grande Valley Audubon Society pushed for the project that will “scrub” the parking lot’s contaminants.

“We advocated for that project for quite some time,” said Sue Griffin, an official with the organization. “As a volunteer at the park, it’s great to see this project come to reality.”

Along with the project, Mendez said, the city will double the size of the park’s five ponds.

“It will attract wildlife and improve the quality of the water of the arroyo,” Mendez said.

As part of the project, he said, Cameron County crews will pave the park’s gravel parking lot.

Residents like Griffin helped turn the 40-acre park, built over a landfill, into a thriving natural showcase that became part of the World Birding Center.

Now, city officials have applied to the General Land Office for grant money to fund construction of a welcome center that schools could use as a science classroom, Mendez said.

“This is going to be a major step to bring the park up to the standards of other parks in the Harlingen area,” Griffin said.